1. Field of the Invention
The present invention relates to an apparatus for use in the oil well industry, and, more particularly, to a drop ball catcher apparatus for use with downhole tools in oil well drilling and installation operations.
2. Description of the Prior Art
Drop ball mechanisms are used in oil well drilling and installation operations typically to activate downhole tools. In U.S. Pat. No. 6,467,546, for example, a drop ball mechanism is disclosed for use in activating downhole tools and devices, namely: float equipment, flapper valves, squeeze tools, inflatable packers, running tools, adaptors, test tools, and the like. The drop ball apparatus of the '546 patent includes a drop ball and a yieldable ball seat. The yieldable ball seat is attached to an inner sleeve arranged within a downhole tool. The downhole tool is generally suspended in a borehole on a tubular string such as a drill string. To activate the downhole tool, a ball having a diameter larger than the diameter of the yieldable seat is dropped from the surface through the tubular string and into the downhole tool where it lands in the yieldable seat. The ball plugs the yieldable seat such that communication through the seat is interrupted. Drilling fluid pressure is then increased above the ball to displace the inner sleeve axially downward thereby activating the tool. In one embodiment of the '546 patent, shifting the inner sleeve axially downward launches a second ball having a diameter larger than the drill string to activate a set of flapper valves in a float collar. Once the tool is activated, drilling fluid pressure is again increased above the first ball to force the ball through the yieldable seat and out of the tool to the bottom of the borehole.
In U.S. Pat. No. 6,155,350, assigned on its face to Baker Hughes Inc., a ball seat mechanism is disclosed for use in downhole oil well tools which are also actuated by pressure build-up means. The ball seat mechanism of the '350 patent includes a ball and a ball seat supported by a rupture disc and attached to a tubular string by a set of shear pins. To actuate the downhole tool, the ball is dropped through the tubular string and into the seat to obstruct passage through the seat. Pressure is then increased by means at the surface to a predetermined level to break the rupture disc and thus shear the shear pins. The ball and seat are then displaced from the tubular string to reestablish passage.
In U.S. Pat. No. 5,960,881, a yieldable ball seat is disclosed for shifting a diverter tool used to faciliatate surge pressure reduction while running a casing liner down a borehole. The ball seat of the '881 patent is designed to yield at a particular pressure. To shift the surge pressure reduction diverter tool, a ball is dropped through a drill string to land in the yieldable seat. Drilling mud is then pressurized to a first predetermined level above the ball to shift the diverter tool from an open port position to a closed port position. Next, the drilling mud is pressurized to a second predetermined level above the ball to force the ball through the yieldable seat and out of the casing liner to land at the bottom of the borehole.
While current drop ball systems—such as those described above—provide a reliable means for actuating downhole tools, these systems do not account for the drop ball itself once the tool has been activated. Rather, in current drop ball-actuated systems, the drop ball is displaced from the downhole tool where it falls to the bottom of the wellbore. However, at the bottom of the wellbore, the drop ball becomes an obstacle for the drill bit to break up as drilling operations are resumed. This of course expends valuable time and resources.
Accordingly, the oil well industry would find desirable a drop ball apparatus for activating a downhole tool while promoting drilling operation efficiency by minimizing the proliferation of downhole debris caused by ejecting the drop ball into the wellbore. This novel and useful result has been achieved by the present invention.